This invention relates to sediment cleaning and anti-sedimentation methods and devices and consists particularly in novel, more efficient means for ultrasonically cleaning objects immersed in a fluid, including tube bundles in heat exchangers.
There are many methods and apparatus for acoustically cleaning objects immersed in a fluid. Ultrasonic energy is propagated toward the object in the fluid and the acoustic energy impinges on the surface of the object where such energy loosens sedimentation and suface material to clean the object surface. However, in cleaning an object having many irregular surfaces, acoustic energy quite often fails to clean the surface because the acoustic wave trains arrive at regular, spaced intervals and often miss certain surface areas of the object.
The operation of various pipes and tubes and vessels including heat exchangers is routinely impeded by the buildup of sedimentation in and around internal surfaces and components causing restriction of flow and impediment of enthalpy or both. Devices using acoustic-type energy to resist or remove sedimentation have been suggested. In such devices, a portion of energy is imparted to tubes and other walls encountered and to molecules and particles in suspension or solution in the fluid. If the imparted energy density is less than the deposition energy of suspended or dissolved particles and/or the binding energy of deposited particles, deposition restrain and/or dislodgement of sediment particles will be less efficient in accordance with the laws of statistics. If the imparted energy density exceeds such sedimentation rate and/or binding energy, sedimentation will be prevented and existing sediment more rapidly dissipated.
However, the efficiency of prior art acoustic devices is limited, and, moreover, there is a limit to the power which can be applied to the transducer because of the so-called cavitation effect in the fluid. While composite wave devices have been suggested, these utilize resonance effect and produce resultant standing wave patterns so that the application of augmented wave intensity is limited.